* 
HINTS FOR OFFICERS IN THE DETECTION OF PRECIOUS STONES. 15 
which he was sending out to an officer in Heypt, who wished to 
make a present to the late Khedive. 
It ought to be generally known—but it is not—thatin cool climates 
like that of England, it is quite impossible to mistake pastes for stones. 
You have only to touch them with the tip of your tongue. All stones 
are first-rate conductors of heat and feel intensely cold to the tongue 
(as arule the denser they are the colder they feel) ; paste (a glass of 
great brilliancy, with a lot of lead in it, coloured to represent different 
gems) is a poor conductor, and warm compared with stones. <A single 
experiment will be quite sufficient to enable anyone to tell astone for ever 
after. I always keep some pastes by me, with my collection of precious 
stones, in order to illustrate this fact to visitors. They generally go 
home and “lick” their jewels; and occasionally find, like Solomon, 
that ‘‘ he that increaseth knowledge increaseth sorrow ! ” 
The more lead you put into glass the brighter will the latter be, 
and the softer it will become. You can almost dig the point of a pen- 
knife into a really brilliant paste. I got a parcel of topazes from a 
Leeds firm once, and amongst them was the most brilliant gem I ever 
saw. It was nearly, if not quite, equal to a yellow diamond in refrac- 
tive power. Alas! it was as soft as fluor-spar, and warm to the 
tongue. I tried for days to persuade myself that it might be real, but 
as I found its specific gravity over 4 and therefore it could—if a stone 
—be only an oriental topaz of hardness 9! I finally sent it back. 
The dealer insisted it was genuine, and wrote that he had sold it to a 
customer for 12s. 6d. I have no doubt he did, and that it was worth 
more in the market than any real topaz—of which you can now buy 
good cut crystals for a shilling or two! 
You cannot mistake a cut garnet for a ruby. Looked at with the 
light behind you, the garnet always has a blackness that is quite 
absent in the ruby. Try the experiment. Some spinels are more like 
rubies. Spinels are much used in cheap rings. 
If anyone has a yellowish “off colour” diamond, which he wishes 
to improve for his own personal use, he can easily do so by a process 
invented by a Frenchman several years ago. ‘The inventor came over 
to England with a lot of “improved” diamonds, and did a truly 
glorious trade. He sold some £5000 worth before the jewellers dis- 
covered the dodge. I think it was discovered in the end by the 
accident of a stone falling into some alcohol. Now-a-days no diamond 
buyer would purchase a stone without trying the effect of spirits of 
Wine upon it, so that it can do no harm to disclose the secret. 
Take a blue aniline copying ink pencil and scrape off with a pen- 
knife a shaving or two. Moisten with water, which will make a fine 
blue solution, with which paint the back of your stone delicately with 
a camel’s hair brush. You need not put on more than an invisible 
layer of colour. When it dries it should be so thin as to be quite 
imperceptible to the naked eye. The stone will now have lost all trace 
of yellowness, and look like a gem of the first water. It is a most 
curious experiment. Dipping in alcohol removes the colouring matter 
at once. 
The worth of really noble gems depends so much on infinitesimal 
